JPH10190496A - Interference canceler and pseudo-deciding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve pseudo-decision precision in a deciding part in a multistage type interference canceler and a pseudo-deciding method. SOLUTION: An interference canceler has interference canceler units ICU1 to ICUk which have an inverse diffusion processing part 1 that includes an inverse diffusing device 6 and a channel estimating device 7, a 1st synthesizing part 2, a deciding part 3, a diffusion processing part 4 that includes a diffusing device 10 and a 2nd synthesizing part 5. In such cases, the part 3 has a comparator 8, a hard deciding & soft deciding device 9, compares the amplitude sum of receiving symbol vectors from the part 2 with the amplitude sum of channel estimated values from the device 7 through the comparator 8, switches hard decision and soft decision for the receiving symbol vectors in the device 9 in accordance with the comparison result and performs a pseudo-decision output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multistage interference canceller and a tentative decision method in a CDMA communication system. DS-CDMA (Direct Sequence C
2. Description of the Related Art A digital mobile radio system to which an ode Division Multiple Access (direct spread spectrum code division multiple access) system is applied is known. In such a system, an interference canceller would be used to improve the signal power to interference power ratio (SIR). This interference canceller includes a determination unit that performs a temporary determination of a user channel, and it is desired to improve the determination accuracy in the determination unit.

[0002]

2. Description of the Related Art In a CDMA system, interference from other users due to cross-correlation between spreading codes is reduced,
Various interference cancellers for improving the signal power to interference power ratio (SIR) have already been proposed. In this case, a multi-stage interference canceller having a plurality of stages for generating an interference replica and subtracting the same from a received signal is considered promising.

FIG. 7 is an explanatory diagram of a conventional multi-stage interference canceller, which includes a first stage, a second stage,
.. Shows a case where the m-th stage is cascade-connected, and each stage includes an interference canceller unit 71 and a combining unit 72. Also interference canceller
Unit 71 (ICU _{1,1 to} ICU _{1 , k} , ICU _2,1 to
ICU _{2, k} ,... ICU _{m, 1 to} ICU _{m, k} ) indicate stage numbers _{1 to m} and user numbers 1 to k.

[0004] In the first stage, the received signal R ₀ is converted into interference canceller units ICU _{1,1 to} ICU for the user.
_1, is input to the _k, the interference replica signal s _{1, 2} ~s 1, _k and the interference residual estimation signal d _{1, 1} to d 1, _k is outputted, interference residual estimation signal d _{1, 1} to d _{1 , k} are combined and subtracted from the received signal R ₀ to output an error signal e ₁ .

In the second stage, the interference signal canceller units ICU _{2,1 to} ICU _{1, k} corresponding to the user, the error signal e ₁ from the synthesizer 72 of the first stage, and each of the interference canceller units ICU _1,1 ~ ICU _{1, k} , the interference replica signals s _1,2 -s _{1, k} are input, and the interference replica signals s _2,1 -s _{2, k} and the interference residual estimation signal d _2,1 -d _{2 , k}
Is output, and the interference residual estimation signals d _{2,1 to} d _{2, k} are combined and subtracted from the error signal e ₁ to obtain the error signal e ₂
Is output.

[0006] Similarly, at the m-th stage, the error signal e _m-1 from the previous stage of the synthesis section, interference from the preceding stage interference canceller unit replica signal s _m-1,1 ~s _{m-1 , k}
Are input, and interference residual estimation signals dm _{, 1 to} dm _{, k} and interference replica signals sm _{, 1 to} sm _{, k} are output. Therefore, an interference replica signal from which interference between users has been removed according to the processing of each stage is obtained.

FIG. 8 is an explanatory view of a conventional interference canceller unit. FIG. 8A shows a main part of each interference canceller unit 71 in FIG.
The case of a three-finger configuration for synthesis is shown.
4 shows an example of a signal space when the PSK modulation method is applied.
In the figure, 81 is a despreading processing unit, 82 is a synthesizing unit, 8
3 is a determination unit, 84 is a spreading processing unit, 85 is a combining unit, 86 is a despreader, 87 is an adder, 88 is a multiplier, 89 is a channel estimator, 90 is a multiplier, 91 is an adder, and 92 is an adder. 2 shows a diffuser.

The error signal e _{m-1,1 at the previous} stage (received signal R _{0 in} the case of the first stage) and the interference replica signal s at the previous stage
_{m−1, k} (zero in the case of the first stage) is input to the despreading processor 81 corresponding to the delay profile of the received signal (corresponding to the path), and despreading demodulation is performed by the despreader 86 using the spreading code. Is done. The input signal R _{0 in} this case is input to the interference canceller in a state synchronized with the spreading code.

[0009] The despread demodulated signal and the preceding interference replica signal (zero in the first stage) are added by an adder 87 to generate an _i- th path received symbol vector R _i . The received symbol vector R _i of the i-th path is input to the channel estimator 89, and outputs an estimated value { _i } of the channel (fading vector) of the i-th path.

[0010] and received symbol vector R _i is at the multiplier 88 multiplies the complex conjugate xi] _i ^ ^* of the channel estimation value xi] _i ^, weighting and phase compensation in proportion to the amplitude of the channel estimates xi] _i ^ Are performed, and the output signal of the multiplier 88 corresponding to the path is subjected to maximum ratio combining in the combining unit 82.

[0011] In the determination unit 83, which performs temporary decision on the received symbol vector ΣR _i ξ _i ^ ^* after synthesis, input the error signal from the last stage of the interference canceller and the interference replica signal Then, the user symbol is determined in the receiving processing section that performs the processing. The determination unit 83 outputs the estimated information symbol vector Z _s ^ by the received symbol vector ΣR _i ξ _i ^ ^* hard decision after combining. Diffusion processing unit 8 for this estimated information symbol vector Z _s
In fourth multiplier 90 multiplies the channel estimation value xi] _i ^, and outputs the interference replica signal s _m of each _path, and generates a _k to the next stage.

An adder 91 subtracts the preceding-stage interference replica signal s _{m-1, k} from the interference replica signal s _{m, k of} each path in an adder 91, and outputs the output signal of the adder 91 to a spreader 92.
In step (2), the spread output signals of the respective paths are combined by a combining unit 85 to output an interference residual estimation signal dm _{, k} .

[0013] By performing the above operations for each and each stage to each user corresponding, progressively error signal e _m approaches zero, and increases the accuracy of interference replica signal, an error signal of the final stage and the interference replica signal By using the rake (RAKE) receiving process, a received signal from which interference between users has been removed can be obtained.

FIG. 8B shows the first quadrant of the signal space surrounded by the I and Q channels Ich and Qch when the QPSK modulation method is applied, and shows the received symbol vector {R _i ξ _i ^{} *} . The case where the hard decision is made to obtain the estimated information symbol vector Z _s示 す is shown. That is, the reception symbol vector ΣR _{i ξ i} ^ ^* of the phase corrected so that the regular phase, the level corresponding to the amplitude sum of channel estimates xi] _i ^ of the estimated information symbol vector Z _s ^ a temporary decision output signal It is assumed that.

[0015]

As described above, in the conventional interference canceller, the interference canceller unit corresponding to each user at each stage is provided with the received symbol vector {R _i } which is rake-combined and output by the combining unit 82. _A judgment unit 83 for judging by inputting _i ＾ ^* is provided. Even if the level is abnormally large, conversely small, or the phase difference is large, as shown in FIG. The judgment output of the symbol vector Z _s ＾ is performed. That is, due to the influence of noise or the like, when the level of the received symbol vector {R _i ξ _i ＾ ^* differs greatly from the estimated information symbol vector Z _s ＾ obtained by hard decision, or when the phase difference is large, etc. becomes as estimated information symbol vector Z _s ^ of unreliable by the temporary decision, by using such a low reliability estimated information symbol vector Z _s ^, interference replica signals and interference residual estimate the next stage Outputting a signal causes a problem of deterioration of interference removal ability. An object of the present invention is to make a highly reliable determination.

[0016]

An interference canceller according to the present invention includes (1) at least a despreader 6 and a channel estimator 7, and further includes a reception signal _R0 or a preceding error signal em _-1 and a preceding stage error signal em _-1 . A despreading processing unit 1 for inputting the interference replica signal sm _-1 and a first signal for synthesizing an output signal of the despreading processing unit 1
, A determining unit 3 for determining an output signal of the combining unit 2, and a spreader 10, and a determination output signal of the determining unit 3 and a channel estimation value from the despreading processing unit 1. And a diffusion processing unit 4 for inputting
Interference canceller unit I and a second combining section 5 a of the output signal combining and outputting an interference residual estimation signal d _m
In an interference canceller having at least CU _{1 to} ICU _k , an interference canceller unit ICU _{1 to} ICU _k
Is a comparator 8 that compares the combined output signal of the first combiner 2 with the channel estimation value from the channel estimator 7.
And a hard decision & soft decision unit 9 for switching between the hard decision and the soft decision of the combined output signal of the combining unit 2 based on the comparison result of the comparator 8
And Therefore, the determination unit 3 can improve the determination accuracy by performing a soft determination when determining that the reliability is low and performing a hard determination when determining that the reliability is high.

(2) The decision unit 3 of the interference canceller unit compares the sum of the amplitude of the received symbol vector from the first combining unit 2 with the sum of the amplitude of the channel estimation value from the channel estimator 7. Hard decision and soft decision based on a level comparison result in which the sum of amplitudes of the received symbol vectors by the comparator 8 is equal to or greater than the sum of amplitudes of the channel estimation values, and a soft decision is made based on other comparison results. Table 9
And That is, if the amplitude sum of the received symbol vector is higher than or equal to the amplitude sum of the channel estimation value, the reliability is high and a hard decision is made. For example, it is determined that the reliability is low and a soft decision is made.

(3) The decision unit 3 of the interference canceller unit determines the sum of the amplitude of the symbol vector received from the first combining unit 2, the sum of the amplitude of the channel estimation value from the channel estimator 7, and this channel estimation. The comparator 8 compares a set value set as a value larger than the sum of amplitudes of the received signals, and the comparator 8 compares the set values. When the sum of the amplitudes of the received symbol vectors is a level comparison result equal to or larger than the set value, the channel 8 The soft decision is performed by changing the level to a level smaller than the amplitude sum of the estimated value, and the hard decision is performed when the level comparison result is smaller than the set value and equal to or larger than the amplitude sum of the channel estimated value. And a hard decision & soft decision unit 9 for performing a soft decision when the comparison result has a small level.

(4) The decision unit 3 of the interference canceller unit determines the sum of the amplitude of the received symbol vector from the first combining unit 2, the sum of the amplitude of the channel estimation value from the channel estimator 7, and the channel estimation. The comparator 8 compares a set value set in advance as a value smaller than the sum of amplitudes of the values, a zero output device that outputs a determination result of zero, and a comparator 8,
Based on the comparison result of the level where the amplitude sum of the received symbol vector is smaller than the set value, a zero determination result is output from the zero output device, and a hard decision is performed based on the comparison result of the level equal to or greater than the amplitude sum of the channel estimation value, A hard decision / soft decision unit 9 for making a soft decision based on a comparison result smaller than the amplitude sum of the channel estimation values and not less than the set value.

(5) The decision unit 3 of the interference canceller unit compares the sum of the amplitude of the symbol vector received from the first combining unit 2 with the sum of the amplitude of the channel estimation value from the channel estimator 7. A comparator, a phase comparator for comparing a hard-decision result of the received symbol vector and a phase difference between the received symbol vector and a preset phase setting value, and the phase difference from the phase comparator is set to The soft-decision is performed by changing the received symbol level to a level smaller than the sum of the amplitudes of the channel estimation values according to the comparison result of not less than the value, and comparing the phase difference from the phase comparator with the comparison result smaller than the set value. Performing a hard decision based on the level comparison result of the amplitude sum of the received symbol vector from the level comparator being equal to or greater than the amplitude sum of the channel estimation value,
And a soft decision is made based on a comparison result in which the phase difference from the phase comparator is smaller than the set value and a level comparison result in which the amplitude sum of the received symbol vector from the level comparator is smaller than the amplitude sum of the channel estimation value. And a hard decision & soft decision unit 9 for performing In this case, when the phase difference is larger than the set value, it is determined that the reliability is low, and the soft decision is performed by reducing the level to improve the decision accuracy.

[0021] The provisional determination method in the interference canceller of the present invention, (6) comprises at least a despreader 6 and the channel estimator 7, and the received signal R ₀ or the preceding stage of the error signal e
despreading processing section 1 for inputting _m-1 and the preceding _- stage interference replica signal sm _-1 ; a first synthesis section 2 for synthesizing an output signal of the despreading processing section 1; A determination unit 3 for determining a signal; a diffusion processing unit 4 including at least a spreader 10 and receiving a determination output signal of the determination unit 3 and a channel estimation value from the despreading processing unit 1; interference canceller unit IC and a second combining section 5 a of the output signal combining and outputting an interference residual estimation signal d _m
In a provisional determination method in an interference canceller having at least U _{1 to} ICU _k , an interference canceller unit I
The determination unit 3 of CU _{1 to} ICU _k is switched between hard decision and soft decision, and the sum of the amplitude of the received symbol vector from the first combining unit 2 and the sum of the amplitude of the channel estimation value from the channel estimator 7 are calculated. By performing a hard decision when the amplitude sum of the received symbol vector is equal to or greater than the channel estimation value,
And performing a soft decision when the sum of the amplitudes of the received symbol vectors is smaller than the channel estimation value.

(7) Interference canceller unit ICU
_{1 to} ICU _k are switched between hard decision and soft decision, and the sum of the amplitude of the symbol vector received from the first combining unit 2 and the sum of the amplitude of the channel estimation value from the channel estimator 7 are The amplitude sum of the channel estimation value is compared with a set value set as a value larger in advance, and when the amplitude sum of the received symbol vector is at a level equal to or higher than the set value,
The soft estimation is performed by changing the level to a level smaller than the amplitude sum of the channel estimation value. When the level is smaller than the set value and equal to or larger than the amplitude sum of the channel estimation value, the hard decision is performed, and the amplitude sum of the channel estimation value is calculated. When the level is smaller, it includes a process of making a soft decision.

(8) Interference canceller unit ICU
_{1 to} ICU _k are switched between hard decision and soft decision, and the sum of the amplitude of the symbol vector received from the first combining unit 2 and the sum of the amplitude of the channel estimation value from the channel estimator 7 are A comparison is made with a preset value that is smaller than the amplitude sum of the channel estimation value, and a determination result of zero is output when the amplitude sum of the received symbol vector is at a level smaller than the setting value, and the channel estimation value And performing a soft decision when the level is smaller than the sum of amplitudes of the channel estimation values and equal to or higher than the set value.

(9) Interference canceller unit ICU
_{1 to} ICU _k are switched between a hard decision and a soft decision, and the phase difference between the hard decision result with respect to the received symbol vector from the first combining unit 2 and the received symbol vector, and a predetermined phase When the phase difference is equal to or greater than the set value, the received symbol level is changed to a level smaller than the amplitude sum of the channel estimation value to perform a soft decision, and the phase difference is A hard decision is made when the amplitude sum of the received symbol vector is less than or equal to the amplitude sum of the channel estimation value, and the amplitude sum of the reception symbol vector is smaller than the amplitude sum of the channel estimation value. It sometimes includes the step of making a soft decision.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram for explaining the principle of the present invention. In each stage, an interference canceller unit ICU _{1 to} ICU _k corresponding to a user comprises a despreader 6 and a channel estimator 7. A processing unit 1, a first synthesis unit 2, a determination unit 3 including a comparator 8 and a hard / soft decision unit 9, a diffusion processing unit 4 including a spreader 10, and a second synthesis unit 5. It has.

A plurality of despreading processing sections 1 and 4 are provided corresponding to the delay profile (multipath) of the received signal, as in the conventional example.
Is the error signal em _{-1 at} the preceding stage (the received signal _R0 at the first stage in the multistage interference canceller).
And an interference replica signal s _m-1 (zero in the first stage) of the preceding stage are input, despread and demodulated by a spreading code in a despreader 6, and the despread demodulated signal is added to the interference replica signal s _{m- 1} is added to become a received symbol vector R _i , a channel estimation value { _i ^} is output from the channel estimator 7, and a complex conjugate { _i ^{} * of the} channel estimation value { _i ^} is multiplied by the received symbol vector R _i. , The first synthesizer 2
And the combined received symbol vector {R _i ^} _i ^{} *} is input to the determination unit 3.

[0027] Also In the comparator 8 of the determination unit 3, channel estimate xi] _i ^ amplitude sum Σ | ξ _i ^ | a, the amplitude sum of composite received symbol vector from synthesizing unit 2 Σ | R _{i ξ i} ＾ ^* ｜
And if Σ | ξ _i Σ | ≦ Σ | R _i ξ _i ＾ ^* |, the hard decision & soft decision unit 9 of the decision unit 3 makes a hard decision, and Σ | ξ _i ＾ |> Σ | R _i ξ _i ^ ^* | for, the amplitude of the vector is held, with soft to output corrected for the phase shift.

The estimated information symbol vector Z _s from the determination section 3 is _converted by the spreading section 4 into a channel estimation value ξ _i.
^ Was outputted to the next stage as the interference replica signal s _m is multiplied, and by subtracting the interference replica signal s _m from the preceding stage interference replica signal s _m-1, was spread by the spreading code at the diffuser 10, the synthesized by the second synthesis unit 5 outputs an interference residual estimation signal d _m.

Therefore, by performing a soft decision on a received symbol vector having a low level and poor reliability,
Decision errors are smaller than in the case of performing hard decision, and the accuracy of the interference replica signal can be improved.

2A and 2B are explanatory diagrams of the first embodiment of the present invention. FIG. 2A shows an interference canceller unit corresponding to each user at each stage, and FIG. 2B shows a case where a QPSK modulation method is applied. 1 shows an example of the first quadrant of the signal space of I and Q channels Ich and Qch. In the figure, 11 is a despreading processing unit, 12 is a first synthesis unit (部), 13 is a judgment unit,
4 is a spreading unit, 15 is a second combining unit (Σ), 16 is a despreader, 17 is a channel estimator, 19 is a spreader, 20 is an adder, 21 and 22 are multipliers, and 23 is an adder. , 24, 2
Reference numeral 5 denotes a combining unit (Σ).

The error signal e _{m-1 at} the previous stage (the received signal R _{0 in} the case of the first stage) and the interference replica signal s at the previous stage
_{m-1, j} (zero in the case of the first stage) is input to the despreading processing unit 11 corresponding to the delay profile of the received signal (corresponding to the path i) as in the conventional example. And demodulated by a spreading code. The input signal R _{0 in} this case is input to the interference canceller in a state synchronized with the spreading code.

The despread demodulated signal and the preceding interference replica signal (zero in the first stage) are added by the adder 20 to generate a received symbol vector R _i of the i-th path. The received symbol vector R _i of the i-th path is input to the channel estimator 17 to output an estimated value { _i } of the channel (fading vector) of the i-th path.

[0033] received symbol vector R _i is at the multiplier 21 multiplies the complex conjugate xi] _i ^ ^* of the channel estimation value xi] _i ^, weighting and phase compensation in proportion to the amplitude of the channel estimates xi] _i ^ Is performed, and the output signal of the multiplier 21 corresponding to the path i is subjected to the maximum ratio combining (rake combining) in the combining unit 12.
I do.

[0034] The combining unit 24, the amplitude sum of the received symbol vector ^{_{Σ | R i ξ i ^ *}} | and requests, R _i ξ _i ^
The absolute value of ^* will be synthesized. The synthesizing unit 25, the amplitude sum of channel estimates _{ξ i ^ Σ | ξ i ^} | and requests, will synthesize the absolute value of the channel estimate xi] _i ^. Then, the amplitude sum of the received symbol vector {| R _i }
_i ＾ ^* | and the sum of amplitudes of the channel estimation values Σ | ξ _i ＾ |

The decision unit 13 includes a comparator and a hard decision / soft decision unit as in the decision unit 3 of FIG.
Channel estimate from 5 ξ _i ^ of the amplitude sum Σ | ξ _i ^ |
And the amplitude sum 受 信 of the received symbol vector from combining section 24
| R _i ξ _i ＾ ^* | is compared by a comparator. If the comparison result is Σ | ξ _i ＾ | ≦ Σ | R _i ξ _i ＾ ^* |, a hard decision is made, and Σ | ξ _i ＾ _{|> Σ | R i ξ i} ^ * | case will the amplitude of the vector is held, to perform the soft decision of the output obtained by correcting the phase shift, and controls the hard decision and a soft decision unit .

The estimation information symbol vector Z _sか ら from the determination unit 13 is input to the spreading processing unit 14 corresponding to the despreading processing unit 11, and is multiplied by the channel estimation value { _i } by the multiplier 22. interference replica signal s _m, the _j outputs to the next stage, and the interference replica signal s _m, subtracts the interference replica signal s _{m-1, j} of the preceding from _j, spread by spreading codes at the spreading section 19 , And outputs an interference residual estimation signal dm _{, j} to the next stage.

Therefore, as shown in FIG.
_{ξ i ^ | ≦ Σ | R} i ξ i ^ * | For, normal phase corrected estimated information symbol vector Z _s ^ is temporary decision output signal. In the case of Σ | ξ _i ＾ |> Σ | R _i ξ _i ＾ ^* |, since the level is low and the reliability is poor,
The amplitude is maintained, and the phase is corrected as an estimated information symbol vector. Accordingly, the level is low, if the unreliable holds synthesized received symbol vector R _i ξ _i ^ ^* amplitude of the estimated information symbol vector only the phase corrected Z _s ^ is temporary decision signal. Therefore, when the reliability is poor, it is output as an estimated symbol vector Z _sの in a low level state, thereby preventing erroneous determination in a subsequent stage and improving the accuracy of the interference replica signal and the interference residual estimation signal. can do.

FIG. 3 is an explanatory diagram of a judgment unit according to the first embodiment of the present invention. FIG. 3A shows a main part of the structure of the judgment unit.
(B) shows an example of the signal space as in (B) of FIG. The (12) is first received symbol vector ΣR after rake synthesis by the synthesis unit 12 _{i ξ i} ^ ^*, or (24) an amplitude sum of the received symbol vector after rake synthesis by the synthesis unit 24 Σ | R _i ξ _i ＾ ^* |, and (25) is the synthesizing unit 25
Is the sum of the amplitudes of the channel estimation values Σ | ξ _i ＾ |

The determination unit 13 includes a hard / soft decision unit 31
And a level comparator 32. The level comparator 32
Is the amplitude sum 受 信 | R _i ξ _i ＾ ^* | (24) of the received symbol vector rake-combined by the combining unit 24 in FIG.
And the sum of the amplitudes of the channel estimation values by the combining unit 25 Σ | ξ _i
＾ | (25).

Then, in the hard / soft decision unit 31,
For a received symbol vector ^{_{R i ξ i ^ * (12}} ) that rake synthesis by in combining unit 12 in FIG. 2, the comparison result of the level comparator _{32, Σ | ξ i ^ |} ≦ Σ | R i ξ i ^ *
In the case of |, a hard decision is made, and Σ | ξ _i ＾ |> Σ | R _i ξ
_In the case of _i軟^* |, soft decision is performed.

That is, as shown in FIG.
_i＾ | ≦ Σ | R_iξ_i＾^*The received symbol vector for |
Tor R_iξ_i＾^*About the normal phase by hard decision
And the sum of the amplitudes of the channel estimates ξ | ξ_i＾ |
Estimated information symbol vector Z of corresponding level_sTentatively
Output as judgment, and Σ | ξ_i＾ ｜ ＞ Σ ｜ R_iξ_i＾ ^*
| Received symbol vector R for |_iξ_i＾^*about
Corrects phase because of low level and poor reliability
However, the amplitude is kept as it is.
Vol vector Z_s＾ is output as a tentative judgment.

FIG. 4 is an explanatory view of a judgment section according to a second embodiment of the present invention. FIG. 4A shows a main part of the configuration of the judgment section.
2B illustrates an example of a signal space similar to that of FIG.
The decision unit 13 has a hard decision & soft decision unit 31a and a level comparator 32a. The level comparator 32a is the sum of the amplitudes of the received symbol vectors rake-combined by the combining unit 24 in FIG. R _i ξ _i ＾ ^* | (24) and the amplitude sum of the channel estimation value by the combining unit 25 Σ | ξ _i ＾ | (2
5) is compared with the set value A. The set value A, the amplitude sum Σ channel estimate | set in advance as a value greater than | xi] _i ^.

[0043] Then, a hard decision & soft decision unit 31a, the reception symbol vector ΣR _i ξ _i ^ ^* for by synthesis section _{12, Σ | ξ i ^ |} ≦ Σ | R i ξ i ^ * | < hardness when A The judgment result is output and Σ | ξ _i ＾ |> Σ | R _i ξ _i ＾ ^* |
, The soft decision result is output, and A ≦ {| R _i ξ _i ＾
At the time of ^* |, the soft decision is made with the amplitude smaller than the sum of the amplitudes of the channel estimation values.

[0044] That is, the rake combining after reception symbol vector ΣR _{i ξ i} ^ ^*, if the vector indicated by b in the signal space of FIG. 4 (B), the amplitude sum Σ of the received symbol vector | R _i ξ _i For ＾ ^* |, Σ | ξ _i ＾ | ≦ Σ | R _i
Ａ _i ＾ ^* | <A, the estimated information symbol vector Z ₁に よ り is output as a tentative decision by hard decision, and c
In the case of the vector shown by, Σ | ξ _i ＾ |> Σ | R _i ξ _i ＾
^* | Because made, the soft decision by the estimation information symbol vector Z ₂ ^ a temporary decision output, and when the vector indicated by _{a, A ≦ Σ | R i} ξ i ^ * | from the amplitude of the channel estimates Perform a soft decision by changing to a level smaller than the sum,
For example, the estimated information symbol vector Z ₂と す る is used as the tentative determination output.

[0045] Therefore, corresponding to when the received symbol vector ΣR _i ξ _i ^ ^* of the amplitude sum after rake combining may exceed the set value A, the noise or the like is abnormally levels are superimposed in equiphase was higher However, since the reliability is reduced, by performing a soft decision by changing to a level smaller than the amplitude sum of the channel estimation value, the decision error error can be suppressed small, the interference replica signal and the interference residual estimation signal and Accuracy can be improved.

FIG. 5 is an explanatory diagram of a judgment unit according to the third embodiment of the present invention. FIG. 5A shows a main part of the structure of the judgment unit.
2B illustrates an example of a signal space similar to that of FIG.
The determination unit 13 includes a hard / soft decision unit 31b, a level comparator 32b, and a zero output unit 33.
2b, the amplitude sum of the received symbol vector obtained by rake synthesis by in combining unit 24 in FIG. _{2 Σ | R i ξ i ^} * | (2
4) and the sum of the amplitudes of the channel estimation values by the combining unit 25 |
{ _i } | (25) is compared with the set value B. The setting value B, the amplitude sum Σ channel estimate | set in advance as a value smaller than | xi] _i ^.

[0047] Then, a hard decision & soft decision unit 31b is received symbol vector ΣR _i ξ _i ^ ^* for by synthesis section 12, in comparison to the level comparator 32b, Σ | ξ _i
When ＾ | ≦ Σ | R _i ξ _i ＾ ^* |, an estimated information symbol vector obtained by hard decision is used as a tentative judgment output, and Σ | ξ _i ＾ |>
When Σ | R _i ξ _i ＾ ^* |> B, the estimated information symbol vector by soft decision is used as a tentative decision output, and B> Σ | R _i ξ
_{When i} ＾ ^* |, zero is output from the zero output device 33 as the provisional judgment output.

[0048] That is, ^* rake combining after reception symbol vector ΣR _i ξ _i ^ is, when the vector indicated by d in the signal space of FIG. 5 (B), the amplitude sum Σ of the received symbol vector | R _i ξ _i For ＾ ^* |, Σ | ξ _i ＾ | ≦ Σ | R _i
ξ _i ＾ ^* |, the estimated information symbol vector Z ₁に よ り is output as a tentative decision output by hard decision. In the case of the vector indicated by e, Σ | ξ _i ＾ |> Σ | R _i ξ _i ＾ ^*
|> B, the estimated information symbol vector Z ₂ ＾ is used as a tentative decision output by soft decision. In the case of a vector indicated by _{f, B> Σ | R i} ξ i ^ * | because made, the zero output device 3
Zero from 3 is used as the temporary judgment output.

[0049] Therefore, if the size of the received symbol vector ΣR _i ξ _i ^ ^* of the amplitude sum after rake synthesis is less than the set value B, because there is low reliability, the estimated information symbol vector is outputted as zero. As a result, it is possible to reduce the determination error and improve the accuracy of the interference replica signal and the interference residual estimation signal.

FIG. 6 is an explanatory diagram of a judgment unit according to a fourth embodiment of the present invention. FIG. 6A shows a main part of the structure of the judgment unit.
2B illustrates an example of a signal space similar to that of FIG.
The decision unit 13 has a hard decision & soft decision unit 31c, a level comparator 32c, and a phase comparator 34. The level comparator 32c is a rake-combined received symbol by the combining unit 24 in FIG. Sum of vector amplitudes | R _i ξ _i ＾ ^* |
(24) and the sum of the amplitudes of the channel estimation values 合成 | ξ _i ξ | (25) by the combining unit 25 are compared.

[0051] The phase comparator 34, the received symbol vector ΣR after rake combining _{i ξ i} ^ ^* and hard decision & soft decision device 3
1c obtains a phase difference theta between hard decision result in the compare this with the phase difference theta, and a setting value theta _A. This set value θ _A is
This is set in advance as a range in which the phase difference with respect to the normal phase in each quadrant can maintain the certainty.

Then, the result of comparison between the level comparator 32c and the phase comparator 34 is input to the hard decision / soft decision unit 31c.
It switches between hard decision and soft decision.
The soft decision unit 31c calculates は | ξ _i ＾ | ≦ Σ | R _i ξ _i ＾
^* | And the comparison result of θ <θ _A makes a hard decision,
_{Σ | ξ i ^ |> Σ} | R i ξ i ^ * |, and performs soft decision when the result of comparison θ <θ _A. And θ ≧ θ _A and Σ | ξ
_{i ^ | ≦ Σ | R i} ξ i ^ * | For the comparison result, performs soft decision as smaller amplitude than the sum of the channel estimates.

[0053] That is, ^* rake combining after reception symbol vector ΣR _i ξ _i ^ is, when the vector indicated by g in signal space of FIG. 6 (B), the amplitude sum Σ of the received symbol vector | R _i ξ _i For ＾ ^* |, Σ | ξ _i ＾ | ≦ Σ | R _i
ξ _i ＾ ^* |, and the phase difference θ between this vector g and the estimated information symbol vector Z ₁に よ る by hard decision is within the set value θ _A , so it is determined that the reliability is high. Then, the estimated information symbol vector Z ₁ } of the hard decision result is used as the tentative decision output.

Also, the received symbol vector Σ after rake combining
When R _i ξ _i ＾ ^* is a vector indicated by h, the amplitude sum Σ | R _i ξ _i ＾ ^* |
Σ | ξ _i ＾ |> Σ | R _i ξ _i ＾ ^* |
The phase difference θ between the vector h and the hard-decision estimated information symbol vector Z ₁と is within the set value θ _A , the reliability is determined to be low, and the soft-decision estimated information symbol vector Let Z ₂ } be the provisional judgment output.

Also, the received symbol vector レ イ after rake combining
If R _i ξ _i ＾ ^* is a vector represented by k, the amplitude sum Σ | R _i ξ _i ＾ ^* |
Σ | ξ _i ＾ | ≦ Σ | R _i ξ _i ＾ ^* |
And the phase difference between the estimated by vector k and the hard decision information symbol vector Z ₁ ^ theta is, will exceed the set value theta _A. In this case, even if the amplitude sum of the vector k exceeds the amplitude sum of the channel estimation value, the phase difference θ is large,
It is determined that the reliability is low, and the estimated information symbol vector Z ₂の of the soft decision result is set as the temporary decision output as an amplitude smaller than the amplitude sum of the channel estimation values.

Therefore, the amplitude sum of the received symbol vector Σ
| R _i ξ _i ＾ ^* | is the sum of the amplitudes of the channel estimates Σ | R _i
Even if it is larger than { _i ^{} *} |, the estimated information symbol vector Z ₁ ^{} of} the hard decision result and the received symbol vector {R _i
If the phase difference θ from ξ _i ＾ ^* exceeds the set value θ _A , it is determined that the reliability is low because the vector is close to the adjacent quadrant, and in that case, it is determined from the sum of the amplitudes of the channel estimation values. A soft decision is made by changing the level to a small level, and a decision error due to a large phase difference in the quadrant can be suppressed. Therefore, it is possible to improve the accuracy of the interference replica signal and the interference residual estimation signal.

The present invention is not limited to the above-described embodiments, but can be variously added and changed, and the embodiments can be combined. For example, in the case of the sum of the amplitudes of the received symbol vectors at a level exceeding the set value A by the set values A and B, the amplitude is changed to a small level to perform a soft decision, and In the case of the sum, it may be configured to output zero.

[0058]

As described above, according to the present invention, in the interference canceller having a plurality of interference canceller units, the judgment unit 3 of each interference canceller unit includes the comparator 8 and the hard decision & soft decision unit. 9 and the first combining unit 2
By comparing the sum of the amplitude of the received symbol vector from the sum with the sum of the amplitudes of the channel estimation values,
Judges whether the received symbol vector is highly reliable or not, and makes a hard decision when it can be judged that the reliability is high, and makes a soft decision or a soft decision by reducing the level when it is judged that the reliability is low. , and the thus, it is possible to reduce the decision error, it is possible to improve the estimation accuracy of the interference residual estimation signal d _m and the interference replica signal s _m outputted from the interference canceller unit. Thereby, there is an advantage that the interference canceling characteristics in the interference canceller can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is an explanatory diagram of the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a determination unit according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram of a determination unit according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram of a determination unit according to a third embodiment of the present invention.

FIG. 6 is an explanatory diagram of a determination unit according to a fourth embodiment of the present invention.

FIG. 7 is an explanatory diagram of a conventional multi-stage interference canceller.

FIG. 8 is an explanatory diagram of a conventional interference canceller unit.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 despreading processing unit 2 first combining unit 3 determination unit 4 spreading processing unit 5 second combining unit 6 despreader 7 channel estimator 8 comparator 9 hard decision & soft decision unit 10 spreaders ICU _{1 to} ICU _k Interference canceller unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shugaku Kobayakawa 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Hiroyuki Seki 4-chome, Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture No. 1 Fujitsu Limited (72) Inventor Masafumi Tsutsui 4-1-1 Kamikadanaka Nakahara-ku, Kawasaki City, Kanagawa Prefecture Fujitsu Limited

Claims (9)

[Claims] 1. A despreading processing unit including at least a despreader and a channel estimator, and receiving a received signal or a preceding-stage error signal and a preceding-stage interference replica signal, and outputting an output signal of the despreading processing unit. A first combining unit for combining, a determining unit for determining an output signal of the first combining unit, and a spreader, and a determination output signal of the determining unit and a channel estimation value from the despread processing unit And a diffusion processing unit for inputting
A second combining unit that combines the output signal of the spreading processing unit and outputs an interference residual estimation signal, wherein the determining unit of the interference canceller unit includes at least an interference canceller unit having a second combining unit. A comparator for comparing a combined output signal of the first combining unit with a channel estimation value from the channel estimator; and a hard decision of a combined output signal of the first combining unit based on a comparison result of the comparator. An interference canceller having a configuration for switching between soft decision and soft decision. 2. The comparator, comprising: a comparator for comparing a sum of amplitude of a symbol vector received from the first combining unit with a sum of amplitude of a channel estimation value from the channel estimator; A hard decision & soft decision unit for performing a hard decision based on a level comparison result whose amplitude sum of a received symbol vector is equal to or greater than the amplitude sum of the channel estimation value and performing a soft decision based on other comparison results. Item 2. The interference canceller according to item 1. 3. The method according to claim 2, wherein the determining unit calculates the sum of the amplitude of the symbol vector received from the first combining unit, the sum of the amplitude of the channel estimation value from the channel estimator, and a value larger than the sum of the amplitudes of the channel estimation values. A comparator for comparing the set value with a set value, and comparing the set value with the comparator, and when the level sum of the received symbol vector is a level comparison result equal to or greater than the set value, the level is changed to a level smaller than the amplitude sum of the channel estimation value. To perform a soft decision, perform a hard decision when the level comparison result is smaller than the set value and equal to or larger than the amplitude sum of the channel estimation value, and perform a soft decision when the comparison result is a level smaller than the amplitude sum of the channel estimation value. The interference canceller according to claim 1, further comprising a hard decision & soft decision unit. 4. The method according to claim 1, wherein the determining unit calculates a sum of an amplitude of the symbol vector received from the first combining unit, a sum of the amplitudes of the channel estimates from the channel estimator, and a value smaller than the sum of the amplitudes of the channel estimates. A comparator for comparing a preset value as a preset value, a zero output device for outputting a determination result of zero, and a comparison result of a level at which the amplitude sum of the received symbol vector by the comparator is smaller than the set value, The zero output unit outputs a determination result of zero, performs a hard decision based on a level comparison result equal to or more than the amplitude sum of the channel estimation value, and performs a hard decision based on a level comparison result smaller than the amplitude sum of the channel estimation value and equal to or greater than the set value. 4. The interference canceller according to claim 1, further comprising a hard decision & soft decision unit for performing a soft decision. 5. A level comparator for comparing a sum of amplitude of a received symbol vector from the first combining unit with a sum of amplitude of a channel estimation value from the channel estimator; And a phase comparator for comparing a phase difference between the hard decision result and the received symbol vector with a preset phase setting value, and the phase difference from the phase comparator is equal to or greater than the set value and the reception is performed based on the comparison result. A soft decision is performed by changing the symbol level to a level smaller than the amplitude sum of the channel estimation value, and the comparison result in which the phase difference from the phase comparator is smaller than the set value and the comparison result from the level comparator The amplitude sum of the received symbol vector makes a hard decision based on the level comparison result equal to or more than the amplitude sum of the channel estimation value, and the phase difference from the phase comparator is larger than the set value. A hard decision & soft decision unit for performing a soft decision based on a small comparison result and a comparison result of a level where the sum of amplitudes of the received symbol vectors from the level comparator is smaller than the sum of amplitudes of the channel estimation values. The interference canceller according to any one of claims 1 to 4, wherein 6. A despreading processing unit including at least a despreader and a channel estimator, and receiving a received signal or a preceding-stage error signal and a preceding-stage interference replica signal, and outputting an output signal of the despreading processing unit. A first combining unit for combining, a determining unit for determining an output signal of the first combining unit, and a spreader, and a determination output signal of the determining unit and a channel estimation value from the despread processing unit And a diffusion processing unit for inputting
A provisional determination method in an interference canceller including at least an interference canceller unit having a second combining unit that combines an output signal of the spreading processing unit and outputs an interference residual estimation signal; The configuration is such that the determination unit of the unit is switched between hard decision and soft decision, and the sum of the amplitude of the received symbol vector from the first combining unit is compared with the sum of the amplitude of the channel estimation value from the channel estimator. A step of performing a hard decision when the amplitude sum of the received symbol vector is equal to or greater than the channel estimation value, and performing a soft decision when the amplitude sum of the received symbol vector is smaller than the channel estimation value. Judgment method. 7. The apparatus according to claim 1, wherein said determination unit of said interference canceller unit is configured to switch between a hard decision and a soft decision.
Comparing the sum of the amplitudes of the received symbol vectors from the combining unit with the sum of the amplitudes of the channel estimation values from the channel estimator and a set value set as a value larger than the sum of the amplitudes of the channel estimation values, and Is the sum of the amplitudes
When the level is equal to or higher than the set value, a soft decision is performed by changing the level to a level smaller than the amplitude sum of the channel estimation value. 7. The method according to claim 6, further comprising: performing a soft decision when the level is smaller than the sum of amplitudes of the channel estimation values. 8. The apparatus according to claim 1, wherein said determination unit of said interference canceller unit is configured to switch between a hard decision and a soft decision.
Comparing the amplitude sum of the received symbol vector from the combining unit with the amplitude sum of the channel estimation value from the channel estimator and a preset value smaller than the amplitude sum of the channel estimation value. The amplitude sum of the symbol vector outputs a determination result of zero when the level is smaller than the set value, performs a hard decision when the level is equal to or larger than the amplitude sum of the channel estimation value, and is smaller than the amplitude sum of the channel estimation value. 8. The tentative judgment method according to claim 6, further comprising a step of performing a soft decision when the level is equal to or higher than the set value. 9. The apparatus according to claim 1, wherein said determination unit of said interference canceller unit is configured to switch between hard decision and soft decision.
The hard decision result for the received symbol vector from the combining unit and the phase difference between the received symbol vector and a preset phase set value are compared, and when the phase difference is equal to or greater than the set value, the received symbol level is The soft decision is performed by changing the level to a value smaller than the amplitude sum of the channel estimation value, and the phase difference is smaller than the set value, and the amplitude sum of the received symbol vector is a level equal to or larger than the amplitude sum of the channel estimation value. 9. The provisional decision according to claim 6, further comprising the step of: performing a hard decision at a time, and performing a soft decision when the sum of the amplitudes of the received symbol vectors is at a level smaller than the sum of the amplitudes of the channel estimation values. Method.